Electric incandescent lamp



July 23, 1940. J. KUHNE ET AL 2,208,987

ELECTRIC INCANDESCENT LAMP Filed May 18,- 1939 lhventor's Joachim Kljhne', Albert Dresier,

Their Attorrieg.

Patented July 23, 1940 PATENT OFFICE ELECTRIC INOANDESCENT LAND Joachim Kiihne, Berlin-Wilmersdorf, and Albert Dresler, Berlin-Dahlem, Germany, assignors to General Electric Company, a corporation of New York Application May 18,1939, Serial No. 274.440 In Germany May 24, 1938 4 Claims.

Our invention relates in general to electric incandescent lamps comprising a tungsten or other refractory metal filament mounted within a sealed envelope. More specifically, our invention I relates to so-called getters for such lamps, and in particular to getters for lamps containing a gaseous filling at a pressure above atmospheric.

In order to beable to apply a particularly high load to the filament of gas-filled electric incandescent lamps to thereby increase the light yield, a gas filling is frequently used at a pressure in excess of one atmosphere. In such lamps, the glass envelope or bulb is selected as small as possible in order to prevent its bursting. In addition, the bulb may be advantageously formed, above the filament, in the shape of a chimney so that the particles which vaporize oif the filament during lamp operation, will be led away from the filament by the resulting convection currents and will be deposited in the chimneylike part of the bulb.

Lamps as described above have a limited life which is due mainly to the emission of oxygencontaining gases and vapors resulting from the 25 high heating of all wall parts and structural parts. This limitation of lamp life is further caused by the corrosion of the filament which generally consists of tungsten, such corrosion resulting from the formation of oxygen within the 30 bulb.

In order to-avoid the above referred to disadvantage, and consequently to obtain a longer life of gas-filled electric incandescent lamps of the type referred to hereinbefore, there is arranged, according to the invention, in the lower end of the chimney-like part of the bulb, a metal body provided with a getter material which binds oxygen but which is hard to vaporize, such as zirconium. 'The metal body is arranged so close to the filament that during the operation of the lamp, the metal body and the getter material are heated, by means of heat radiation, conduction and convection, to a temperature of more than 500 C., which is sufficient for the reactivity of the getter material. The getter material, which in the cold state practically does not bind oxygen, must in addition be of such a quality, as is the case, for instance, with zirconium, that it neither vaporizes itself at the temperatures occurring within the lamp nor forms volatile compounds with the oxygen. The zirconium oxide which is formed'when zirconium is used is, as

known, particularly heat resistant and has only a negligibly small vapor pressure even at temperatures that are far in excess of 2500 C.

In a lamp constructed according to the invention the traces of oxygen will be rendered positively harmless during the entire life of the lamp for the reason that the getter material, of which a'sumcient quantity must of course be provided, does not vaporize and is therefore constantly ready for action, and also because the getter material does not form any volatile compounds which, by dissociation, might lead to vaporization of the filament.

In order to obtain a particularly high efficacy of the getter material, and a good adhesion thereof to the metal supporting body, the latter is preferably roughened and covered with a layer of pulverulent getter material which subsequently, is securely affixed to the metal supporting body by means of sinterin'g. The metal body, which possesses a high heat conductivity and which carries the getter material, is preferably formed in the shape of a sleeve of woven wire which tapers conically upward, or in the shape of a perforated sheet sleeve, so that the getter material will offer the largest possible surface to the gas flow which is formed in the lamp during operation.

While it is known in itself to provide woven wire fabrics or screens in gas-filled incandescent lamps, these screens, however, heretofore have served only for the purpose of gathering the metal particles that are flung away from the filament directly on the wire fabric, in order to prevent thereby a blackening of the lamp bulb. In order to enhance the deposition of the metal particles on such screens, the wire fabrics have even been connected to electric current conductors so that an electric field, which attracts those metal particles to the wire fabric, was produced between the fabric and the filament. In the lamp according to the invention, part of the vaporized filament particles will be deposited on the metal supporting body for the getter material, since this metal supporting body lies in the path of the rising gasesI However, the main effect of the said body lies in the removal of dangerous oxygen traces, such removal being accomplished by the getter materials which are coated on such body and which have been selected in a predetermined manner and located in predetermined relation to the filament.

Further features and advantages of our invention will appear from the following detailed description and from the accompanying drawing which is an elevation of a gas-filled incandescent lamp comprising our invention.

Referring to the drawing, the lamp there shown comprises a tubular bulb l, consisting of glass, quarts or the like, which is filled with an inert gas such as krypton or argon, or with a krypton-xenon mixture, possibly with an addition of nitrogen. The gas filling has a pressure in excess of one atmosphere, for instance, a pressure of atmospheres when the lamp is cold, which corresponds to a pressure of to atmospheres when the lamp is in operation. Within the lamp is a filament 2 which consists of a tungsten wire coil and which is supported by leading-in orv current supply wires 4 and 5 hermetically sealed in a stem tube 3. -The outer end of leading-in wire 4 is connected to the shell 6, and the outer end of the leading-in wire 5 is connected to the bottom contact I, of a conventional screw-threaded lamp.base. If desired, a bayonet type base may be used instead of a screw-threaded base. In the vicinity of the filament 2, the lamp bulb is provided with a bulging or bulbous part 8 for the purpose of equalizing the temperature. The upper portion of the bulb I is formed with a tubular extension I disposed above the filament 2 and serving as a chimney. In this chimney-like part 8' of the bulb I, and preferably adjacent the lower end thereof, there is located a sleeve-like and preferabiy perforated body 9, such as wire fabric, which tapers upward and which is fastened to leading-in wire 4 by means of a support wire Hi. This hollow frusto-conical metal body or sleeve 9, preferably made of nickel, is coated on the inside and on the outside with a layer of powder consisting of zirconium or a similar material,

hard to vaporize, which is sintered on and which,

in the highly heated state, has a great afflnity for oxygen and which forms a highly heat-resistant oxide by binding the oxygen traces which are liberated from the highly heated glass walls and the structural parts of the lamp.

The filament 2 may be of any desired shape and may be in the form of a single-coiled. filament or a double-coiled, or multiple-coiled filament. The bulb I may consist partly of ceramic or metallic materials, and may be made transparent to light only at a small area opposite the location of the filament. The lamp can further be equipped with a sheet or wire guard surrounding theibulb as a protection against explosions.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric incandescent lamp comprising an envelope containing a gas filling, a refractory metal filament mounted within said envelope, a metal screen member disposed closely adjacent to and above said filament when the lamp is in use, and a coating of difllcultly vaporizable getter material on said member, said getter material, when heated, having a relatively high aflinity for oxygen and forming non-volatile compounds therewith.

2. An electric incandescent lamp comprising an envelope containing a gas filling, a refractory metal filament mounted within said envelope, a metal screen member disposed closely adjacent to and above said filament when the lamp is in use, and a coating of getter material on said member consisting of pulverulent metallic zirconium sintered to the said member.

3. An electric incandescent lamp comprising an envelope containing a gas filling and having a tubular extension at its upper end, a refractory metal filament mounted within said envelope below said tubular extension, a perforated metal sleeve member disposed within said envelope closely adjacent to and above the said filament and in substantial axial alignment with said tubular extension, and a coating of difilcultly vaporizable pulverulent getter material on said sleeve memmr, said getter material, when heated, having a relatively high afllnity for oxygen and forming non-volatile compounds therewith.

4. An electric incandescent lamp comprising an envelope containing a gas filling and having a tubular extension at its upper end, a refractory metal filament mounted within said envelope below said tubular extension, a wire screen in the form of a sleeve disposed within said envelope closely adjacent to and above the said filament and in substantial axial alignment with said tubular extension, and a layer of pulverulent zirconium sintered on said wire screen.

JOACHIM KtTHNE. ALBERT DRESLER. 

